For a display device (specifically, a liquid crystal display device), a wider field of view is usually desirable such that users can view the contents therefrom at various angles. For a personal mobile apparatus, e.g. a mobile phone, personal digital assistant, however, there exits a need to keep others from viewing the contents therefrom due to privacy concerns. In view of this, a liquid crystal display device capable of adjusting effective display viewing field has been continuously developed.
The simplest way to alter the effective display viewing field is, for example, utilization of a polarizing film in a display part of the liquid crystal display device. Another method that electronically adjusts the effective display viewing field according to variation of the gamma characteristic in a vertical electric field type liquid crystal display device of vertical alignment mode, twisted nematic mode or electrically controlled birefringence mode is also proposed. Alternatively, in Japanese patent no. 2007-503603, disclosed is a display device having a pair of panels for controlling the viewing field.
In a horizontal electric field type liquid crystal display device of in-plane switching mode or fringe field switching mode, because the gamma characteristic (y) remains at an ideal value of 2.2, it cannot electronically adjust the effective display viewing field according to variation of the gamma characteristic.